RISC-V at it’s heart is a very simple core standard for new general-purpose processors, making it very simple in theory, but CPUs usually need some extensions for real world use cases. So as well as the core standards the RISC-V organisation also promotes some profiles allowing people to select CPUs with some reasonable compatibility expectations.
Most boards I’m developing on are designed to match the (older) RVA22 profile with (newer) RVA23 being very similar but adding more extensions, which hardware manufacturers are only just now starting to finalise implementations of. So testing my platform with RVA23 will begin some time after those devices become available, with the UR-DP1000 possibly being one of the last major CPU release before everyone standardises on RVA23 (it should already have some of the RVA23 features but not all). The hypervisor/virtualisation extensions which are very rare on current devices should be standard as of RVA23.
Thanks to very heavy standardisation process between the RISC-V organisation and manufacturers, any software designed for RVA22 devices should be almost seamlessly compatible with RVA23 devices (aside from different peripherals on different devices), while for embedded developers some of those RVA22/RVA23 features will be overkill for many products (and my software should work without most of them).
So my current strategy is to support these new features where I can – especially I plan to look into any features relevant for HPC & server use cases – but my software will remain targeted towards cheaper/older CPU models and dev boards. Focusing on new models can also lead to problems like features just not working as expected or not being clearly documented, and earlier versions pre-RVA23 will probably still be much cheaper and more accessible for developers living in tight economic situations, so rest assured I’m very aware of these challenges and will be targeting my software at the most accessible and reliable dev boards. But I will always have both eyes on what’s ahead!
Other CPU Families
Thanks to C and my other development tools being very portable it should be relatively easy to port my whole stack to other CPUs as well, and some legacy AMD64/x86-64 support still exists in the C compiler (mostly based on the LICE code generator from before I extended it with my new backend). I also have a bit of other legacy code from my old OS projects that I could probably draw on for legacy CPU support (and xv6 also provides a version for legacy PCs).
So supporting architectures other than current RISC-V hardware won’t be a priority for my business in the short term but in the longer term support for other CPU families can be added, either by myself or by third-party/open-source distributors.
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